How to debug in docker

Debugging in Docker can be crucial when troubleshooting issues with your containers or applications. Here's a checklist of different ways to debug in Docker, along with examples:

View Container Logs:

Use the docker logs command to view container logs.

docker logs <container_id>

Attach to a Running Container:

Use the docker exec command to attach to a running container and execute commands inside it.

docker exec -it <container_id> /bin/bash

Inspect Container Details:

Use the docker inspect command to get detailed information about a container.

docker inspect <container_id>

Interactive Mode:

Run a container in interactive mode to see real-time output.

docker run -it <image_name> /bin/bash

Docker Compose Debugging:

Use docker-compose to manage multi-container applications.

docker-compose logs
Remote Debugging:

Enable remote debugging inside your application and expose the required ports.
Attach a debugger from your IDE or use tools like gdb.

docker run -p 5005:5005 -it <image_name> java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -jar app.jar

Volume Inspection:

Check if volumes are mounting correctly.

docker inspect -f '{{ .Mounts }}' <container_id>

Health Checks:

Ensure that your Dockerfile includes health checks to monitor container health.

HEALTHCHECK CMD curl --fail http://localhost:8080/ || exit 1

Environment Variables:

Check if environment variables are set correctly.

docker exec <container_id> printenv

Networking:

Verify container network settings.

docker network inspect <network_name>

Container Resource Usage:

Monitor container resource usage.

docker stats <container_id>

Docker Events:

Check Docker events for any issues.

Dockerfile Debugging:

Use RUN commands in your Dockerfile for debugging.

RUN echo "Debugging step: XYZ"
Check Container Health Status:

Inspect the health status of a container.

docker inspect --format='{{json .State.Health}}' <container_id>

Container Inspect for IP Address:

Obtain the IP address of a running container.

docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' <container_id>

Remember to adapt these examples to your specific use case, and use a combination of these debugging techniques based on the nature of the problem you are trying to solve.

Practical Example

Solution